Re: The need to individually switch 50 LED's

[Jim Noble <yahoo-groups@xxxxxxxxxxxxxxxxxx>]

groups@xxxxxxx wrote:

> Hi Group
> I have a need to individually switch 50 LED's from a PC - can anyone
> recommend anything and how to do it?
> I am ofay with soldering, writing code etc, can anyone recommend an
> interface method?
> For those of you who are just wondering why? I have a display cabinet
with
> 50 ornaments and want to individually light them on user selection and
> via a
> script (sad huh?) Thus the wire has to be discreet as well as the
LED's
> shining on each ornament.


Do you need to be able to light more than one at a time? If not, you
could arrange them in an addressable array. Eg, 4 leds could be done
with two 2-bit I/O busses one pulling high, the other pulling low:

_____________
+ve
o        o
/        /
o        o

-(LED)+  -(LED)+
_o \o____/_______/

-(LED)+  -(LED)+
_o \o____/________/

---
-  -ve

49 LEDs would require 7x7, 50 8x7 (or 10x50...)

Individual LEDs are turned on by pulling one +ve bit high, and one -ve
bit low...

(That's what I did about 10 years ago with 256 "spare" LEDs and a
6ft
bit of plastic trunking, to make a hoooj light chaser. Never finished
wiring it up though! :-)

HTH,

Jim



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